Apple Tree Studios

I love my 5DIII autofocus. I've shot about 100 weddings with 5DII bodies, and am on about 15th wedding with my 5DIII. I shot a few weddings on a Nikon D3s last year when I was considering a switch due to the not so good 5DII focus. I loved the Nikon D3s autofocus, but missed the ability to crop that I had on my 5DII, and the skin tones were nicer on my Canon. I decided to stay with Canon. I find the 5DIII faster and more accurate than anything I have ever used. I did a brief, non technical review with pics on my blog here: http://appletreestudiosblog.com/2013/01/04/canon-5d-mark-3-review-for-wedding-photography/

I will be getting another 5DIII soon, the 6D looks great, but I love the 5DIII autofocus. It also make shooting with two cameras easier if they are the same.

Welp, I feel a lot better sticking with a second hand 5DII, that I already have and no problems. My biggest concernif anything was with the 5DII AF but hey, it works, and looks like outside of shooting sports the 5DIII just has better sealed body and handles high ISO/banding a lot better~

Maybe try disabling focus priority on 1st shot. That's fine for AI servo in good light but in low light the 5d3 uses a different focus mode for verifying focus before shutter release. It is more like live view focus but using phase detect. First shot focus priority does cause some delays. If that works better for you, set a custom mode for low light shooting.

Guys we have some progress -- Canon has at least acknowledged a AF issue with 5D3 and 1DX bodies when AF assist is in use. A firmware fix is planned! nothing specific yet about the low light situation where there is no AF assist, but to the extent that the root cause is similar or the same we may see a silent fix to this problem as well

That is good news from Canon. I experienced a similar issue with my 1DX and an EX580II flash. During my last outdoors senior portraits photo shoot, I noticed that my flash was struggling to give enough light for my shots no matter how much I cranked up the FEC or how close I got to the subject. I had to do quite a bit of correction in post production.

A few days later I did a test with my 1D4 and my 1DX and I noticed that with the EX580II flash externally shot inside a softbox on a stick with radio poppers as triggers (always use them), the 580/1D4 combo exposed the scene perfectly and the 580/1DX was waaaaay inconsistent with many under exposed shots. Switching back and forth produced the same results (1D4 was perfect and 1DX was way off).

I now need to figure out what settings or combos are causing this but for now I am shooting all off camera flash with the 1D4. Glad I didn't buy that second 1DX and kept the 1D4.